On Tue, Jun 30, 2009 at 10:40 PM, mqy<meng.qingyou at gmail.com> wrote:
> My test with omgps running shows no failure, with 26954 image files.
> You can add a swap file /partition then test again, to see if limited memory
> causes this problem. I've watched with `vmstat 1`, seen limited memory
> usage.
>> Here is my clues:
>> #1: max current of usb power supply is 500mA, with heavy CPU load, uSD card
> may not get enough power then fails to work.
>> #2: Many people experienced the "lose partition problem" including myself, I
> can remember somebody asked that "why GPS hurt uSD card?".
Ok, I lied a bit. I only tested with tangogps.
But, it was reproducible. If the device freezed or I removed the battery, many
tile maps got unreadable. I couldnt even list some directories or cd into them!
(it rules out heavy CPU load, and not getting enough power)
I already wrote about it about a month ago:
http://lists.openmoko.org/pipermail/community/2009-June/048997.html
So the problem really comes about the insane 75000 files (118MB).
I would really like to tar, ar, zip, etc the dirs containing the invidual tiles.
It seems an easy job! Would be much more managable, speed up
a lot the file copying (copying many small files is several magnitude slower!).
Current directory structure:
OSM/11/1102/715.png
OSM/11/1102/716.png
OSM/11/1102/717.png
OSM/11/1102/718.png
We could simply create an OSM/11/1102.tar file, containing those invidual
files. I bet it would be not slower. I could even imagine some speed boost.
Remember accessing invidual files on a sd card takes time. A lot.
You can try it for yourself, copy to a pendrive your ~/Maps directory.
Now tar the dir (Maps.tar) and copy that singly file to the pendrive.
The result is something like 40sec compared to 6-7min.
So please consider to implement this on-the-fly untaring capability.
Thank you,
Laszlo